Purification and biochemical characterization of 11S globulin from chan (Hyptis suaveolens L. Poit) seeds

Rapid flotation of Microcystis wesenbergii mediated by high light exposure: implications for surface scum formation and cyanobacterial species succession

Increasing occurrences of Microcystis surface scum have been observed in the context of global climate change and the increase in anthropogenic pollution, causing deteriorating water quality in aquatic ecosystems. Previous studies on scum formation mainly focus on the buoyancy-driven floating process of larger Microcystis colonies, neglecting other potential mechanisms. To study the non-buoyancy-driven rapid flotation of Microcystis, we here investigate the floating processes of two strains of single-cell species (Microcystis aeruginosa and Microcystis wesenbergii), which are typically buoyant, under light conditions (150 μmol photons s-1 m-2). Our results showed that M. wesenbergii exhibited fast upward migration and formed surface scum within 4 hours, while M. aeruginosa did not form visible scum throughout the experiments. To further explore the underlying mechanism of these processes, we compared the dissolved oxygen (DO), extracellular polymeric substance (EPS) content, and colony size of Microcystis in different treatments. We found supersaturated DO and the formation of micro-bubbles (50-200 µm in diameter) in M. wesenbergii treatments. M. aeruginosa produces bubbles in small quantities and small sizes. Additionally, M. wesenbergii produced more EPS and tended to aggregate into larger colonies. M. wesenbergii had much more derived-soluble extracellular proteins and polysaccharides compared to M. aeruginosa. At the same time, M. wesenbergii contains abundant functional groups, which was beneficial to the formation of agglomerates. The surface scum observed in M. wesenbergii is likely due to micro-bubbles attaching to the surface of cell aggregates or becoming trapped within the colony. Our study reveals a species-specific mechanism for the rapid floatation of Microcystis, providing novel insights into surface scum formation as well as succession of cyanobacterial species.

Characterization of the Technofunctional Properties and Three-Dimensional Structure Prediction of 11S Globulins from Amaranth (Amaranthus hypochondriacus L.) Seeds

Amaranth 11S globulins (Ah11Sn) are an excellent source of essential amino acids; however, there have been no investigations on the characterization of their techno-functional properties at different pH conditions and NaCl concentrations, which are necessary for food formulations. In this work, we report a new two-step purification method for native Ah11Sn with purity levels of ~95%. LC-MS/MS analysis revealed the presence of three different Ah11Sn paralogs named Ah11SB, A11SC, and Ah11SHMW, and their structures were predicted with Alphafold2. We carried out an experimental evaluation of Ah11Sn surface hydrophobicity, solubility, emulsifying properties, and assembly capacity to provide an alternative application of these proteins in food formulations. Ah11Sn showed good surface hydrophobicity, solubility, and emulsifying properties at pH values of 2 and 3. However, the emulsions became unstable at 60 min. The assembly capacity of Ah11Sn evaluated by DLS analysis showed mainly the trimeric assembly (~150-170 kDa). This information is beneficial to exploit and utilize Ah11Sn rationally in food systems.

Proteomic and computational characterisation of 11S globulins from grape seed flour by-product and its interaction with malvidin 3-glucoside by molecular docking

Grape seed flour by-product (GSBP) is an economic and renewable source of proteins, increasingly being explored due to interesting technological application such as colour protection in rich-anthocyanins beverages. Globulin-like proteins from GSBP were characterised by proteomic and computational studies. MALDI TOF/TOF analysis revealed the presence of two 11S globulins (acid and basic), whose 3D structures have been elucidated for the first time in Vitis vinifera L. grape seeds by using homology models and molecular dynamics. The secondary structure showed 11 α-helices and 25 β-sheets for acid and 12 α-helices and 24 β-sheets for basic 11S globulins. Molecular docking results indicate that both grape seed 11S globulins could establish different types of non-covalent interactions (π-π) with malvidin 3-O-glucoside (wine anthocyanin), which suggest a possible colour protection similar to that occurring in copigmentation phenomenon. These findings provide valuable information of globulin family proteins that could be relevant in food industry applications.

Exploring the Milk-Clotting and Proteolytic Activities in Different Tissues of Vallesia glabra: a New Source of Plant Proteolytic Enzymes

Proteolytic enzymes are widely distributed in nature, playing essential roles in important biological functions. Recently, the use of plant proteases at the industrial level has mainly increased in the food industry (e.g., cheesemaking, meat tenderizing, and protein hydrolysate production). Current technological and scientific advances in the detection and characterization of proteolytic enzymes have encouraged the search for new natural sources. Thus, this work aimed to explore the milk-clotting and proteolytic properties of different tissues of Vallesia glabra. Aqueous extracts from the leaves, fruits, and seeds of V. glabra presented different protein profiles, proteolytic activity, and milk-clotting activity. The milk-clotting activity increased with temperature (30-65 °C), but this activity was higher in leaf (0.20 MCU/mL) compared with that in fruit and seed extracts (0.12 and 0.11 MCU/mL, respectively) at 50 °C. Proteolytic activity in the extracts assayed at different pH (2.5-12.0) suggested the presence of different types of active proteases, with maximum activity at acidic conditions (4.0-4.5). Inhibitory studies indicated that major activity in V. glabra extracts is related to cysteine proteases; however, the presence of serine, aspartic, and metalloproteases was also evident. The hydrolytic profile of caseins indicated that V. glabra leaves could be used as a rennet substitute in cheesemaking, representing a new and promising source of proteolytic enzymes.

Purification and characterization of the major protein isolated from Semen Armeniacae Amarum and the properties of its thermally induced nanoparticles

From the aqueous extract of Semen Armeniacae Amarum, a major protein isolate was purified and characterized as a novel member of the 11S globulin family, which is composed of three polypeptides linked by disulfide bond. Furthermore, the feasibility of using the isolated protein for fabricating nanocarriers was investigated. The results indicate that thermal treatment of the globulin induced the rearrangement of the disulfide bond to form homodimers of acid polypeptides during the formation of nanoparticles. The harvested nanoparticles produced by heat-induced assembly are spherical in shape, with an average size of 92 nm and exhibited low cytotoxicity to L-02 and MDCK cell lines. These nanoparticles are capable to encapsulate paclitaxel, estimated the maximum encapsulation efficiency of paclitaxel loaded to the nanoparticles was 92.6% and the maximum release of paclitaxel was 57.4%. This research suggests that the screening of traditional herbal extracts could provide a novel source of protein nanocarriers.